akari is a top student planning to enter a famous university. during this winter break, she visits an empty school to receive individual lessons from teacher oshima. however, upon arriving at the staff room, oshima makes a request. he asks her to tutor a classmate who has been withdrawing from school, sakushi. although akari is puzzled, she heads to the designated location within the school. but she falls into a trap set by the sadistic teacher and scum, unable to escape the endless cycle of hell and mind control.